When audio or video editors work on large projects such as feature films, the media composition is built up as a set of files, with each file including a part of the work in progress. Each of the files contains about 20 minutes of material, and when arranged sequentially, they make up the entire length of the media composition. In some cases, several files containing different components of the eventual composition are created for a given temporal span. For example, files containing audio tracks of a composition may be created by an audio editor uses a digital audio workstation. Similarly, files containing video sequences may be created by a video engineer using a non-linear video editing system. As the editing proceeds and media is added or removed, files may deviate significantly from 20 minutes-worth of material. When this occurs, the editor adjusts them back to include about 20 minutes-worth of material, since larger files can be unwieldy and harder to navigate during the editing process. This rebalancing process involves moving material from one file to another. Since the editing tools used to create the audio and video only permit a single file to be open at a time, the rebalancing process is cumbersome and time consuming.